1. Field of the Invention
The present invention relates to a temperature control system for air conditioners of the type wherein the proportion of the flow of cool air to be reheated by a heater and the flow of cool air bypassing the heater is controlled by adjusting the opening of an air blend door provided at the inport of the heater so that the temperature of air introduced into the room is adjusted.
2. Description of the Prior Art
In the conventional temperature control system for air conditioners of this type, as disclosed in U.S. Pat. No. 3,315,730, the actual opening of the air blend door is detected by a sensor (e.g., potentiometer) and used together with the setup temperature signal and room temperature signal to calculate the targent opening signal for the air blend door.
One way of measuring the actual opening of the air blend door is based on the difference of the sensor signal from the reference signal which is produced by the sensor when the air blend door is mechanically fully closed (minimum opening) or fully open (maximum opening). In this case, accurate correspondence must have been made between the sensor reference signal and the mechanically full-closed position or full-open position (both will be termed generically "zero-position") of the air blend door.
The inventors of the present invention have proposed to make correspondence between the sensor reference signal and the zero-position of the air blend door by the adjustment of the sensor mount position in the assembling process of the air conditioner such that the sensor provides an output corresponding to the minimum opening position (or maximum opening position) when the air blend door is set to the full-closed position or full-open position. This manual adjustment for the zero-position of the sensor takes a considerable time, and it has been the major reason why the assembling time for the air conditioner cannot be reduced. In addition, during the assembly of the sensor to the zero-position determined by adjustment, the sensor could be moved by an external force, causing the opening of the air blend door to be detected in accordance with an erroneous reference signal, thus resulting in the temperature control based on an erroneous opening signal of the air blend door.